[Differentiation of benign from malignant pulmonary nodules with the digital analysis of computed radiography]

To differentiate benign pulmonary nodules from malignant nodules, digital analysis of computed radiography (CR) was performed retrospectively. A total of 142 histologically or clinically proved cases were studied. Digital analysis was performed using the method of gradient processing reported by Sherrier et al. Gradient number with and without background trend correction and gradient number corrected by L-value were obtained from the raw data of CR. The mean gradient of 93 malignant nodules was significantly different from that of 49 benign nodules. The analysis of gradient number without background trend correction and L-value correction was most sensitive. Seven radiologists evaluated these nodules as to benign or malignant, status, degree of calcification and homogeneity. A correlation was found between the detectability of benign nodules and degree of calcification. In conclusion, CR-gradient analysis is useful as a screening test to differentiate benign nodules from malignant ones.